An electromagnetic device comprises an enclosure, at least one winding in the interior of the enclosure, at least one wireless sensor attached to the winding for sensing at least one property or deficiency of the electromagnetic device and at least one active communication unit comprising transceiving circuitry and at least one antenna, wherein the transceiving circuitry is placed on the exterior of the enclosure and the least one antenna is placed inside the enclosure for communication with the at least one sensor, wherein the at least one sensor comprises at least one sensor attached to the winding, and wherein the at least one sensor attached to the winding is a printed electronic sensor comprising electronics printed on an insulating substrate, where the substrate faces the at least one winding.

A method of manufacturing an electrical device includes providing a composition comprising a mixture of vegetable oil fatty acid esters as a dielectric fluid in an electrical apparatus. The mixture of castor oil fatty acid methyl esters can contain the methyl stearate in a mass content of 1 to 20% to total amount of the mixture, the methyl oleate in a mass content of 1 to 90% to total amount of the mixture, the methyl linoleate in a mass content of 1 to 80% to total amount of the mixture, the methyl palmitate in a mass content of 1 to 50% to total amount of the mixture, the methyl ricinoleate in a mass content of 0 to 4% to total amount of the mixture, and the 10-undecylenic acid in a mass content of 0 to 1%.

A method of manufacturing an electrical device includes providing a composition comprising a mixture of vegetable oil fatty acid esters as a dielectric fluid in an electrical apparatus. The mixture of castor oil fatty acid methyl esters can contain the methyl stearate in a mass content of 1 to 20% to total amount of the mixture, the methyl oleate in a mass content of 1 to 90% to total amount of the mixture, the methyl linoleate in a mass content of 1 to 80% to total amount of the mixture, the methyl palmitate in a mass content of 1 to 50% to total amount of the mixture, the methyl ricinoleate in a mass content of 0 to 4% to total amount of the mixture, and the 10-undecylenic acid in a mass content of 0 to 1%.

A coil assembly including a plurality of substantially planar plates interconnected to define a plurality of electrically conductive windings for surrounding a magnetic core. In one example the invention is used for a magnetic core assembly, including a magnetic core and at least two coil assemblies, the coil assemblies each including a plurality of substantially planar plates interconnected to define a plurality of electrically conductive windings for surrounding the magnetic core.

A coil assembly including a plurality of substantially planar plates interconnected to define a plurality of electrically conductive windings for surrounding a magnetic core. In one example the invention is used for a magnetic core assembly, including a magnetic core and at least two coil assemblies, the coil assemblies each including a plurality of substantially planar plates interconnected to define a plurality of electrically conductive windings for surrounding the magnetic core.

A first plate-like portion is provided with a plurality of first holes extending therethrough in a central axis direction. A second plate-like portion is provided with a plurality of second holes extending therethrough in the central axis direction. The plurality of first holes, the plurality of second holes, a first notch and a second notch overlap one another, to thereby form a flow path which connects one side and the other side of each of a plurality of insulating plates and through which insulating oil can flow in a first direction.

A first plate-like portion is provided with a plurality of first holes extending therethrough in a central axis direction. A second plate-like portion is provided with a plurality of second holes extending therethrough in the central axis direction. The plurality of first holes, the plurality of second holes, a first notch and a second notch overlap one another, to thereby form a flow path which connects one side and the other side of each of a plurality of insulating plates and through which insulating oil can flow in a first direction.

An on-load tap changer head includes: a first region for an insulating fluid of the on-load tap changer to flow; a second region separated from the first region by a wall; and a detector for detecting an increased flow speed of the insulating fluid. The detector includes: a flow flap in the first region configured to tilt from a defined flow speed of the insulating fluid from a first position to a second position; a first magnet secured to the flap such that in the second position of the flow flap, the first magnet is in an immediate vicinity of the wall; a second magnet in the second region in the immediate vicinity of the wall; and a switch in the second region that is operationally coupled to the second magnet such that tilting over of the flow flap from the first position to the second position actuates the switch.

An on-load tap changer head includes: a first region for an insulating fluid of the on-load tap changer to flow; a second region separated from the first region by a wall; and a detector for detecting an increased flow speed of the insulating fluid. The detector includes: a flow flap in the first region configured to tilt from a defined flow speed of the insulating fluid from a first position to a second position; a first magnet secured to the flap such that in the second position of the flow flap, the first magnet is in an immediate vicinity of the wall; a second magnet in the second region in the immediate vicinity of the wall; and a switch in the second region that is operationally coupled to the second magnet such that tilting over of the flow flap from the first position to the second position actuates the switch.

A transformer core frame is provided with a reinforcement structure to form a reinforced transformer core frame. The reinforcement structure comprises one or several reinforcement panels comprising a honeycomb structure and affixed to the transformer core frame. A method of producing a reinforced transformer core frame is also described.